Nintendo has delayed Luigi's Mansion: Dark Moon until the first half of 2013 for the North American market. It's not clear if the Japanese or European market will see that title in 2012. The game was originally scheduled for a "holiday 2012" release.
No reason was given for the delay, but it seems like Nintendo has opt to launch Paper Mario: Sticker Star in the holiday season, instead of taking a risk with Luigi's Mansion: Dark Moon as their big holiday title.
The first Luigi's Mansion was Nintendo's big holiday launch title for their GameCube console back in 2001, but that title didn't give Nintendo the sales boost they was looking for. I'm personally disappointed by the delay, but hopefully they'll use the additional development time to add an extra location or two.
Image Credit: Nintendo